This invention relates generally to an electrostatographic printing machine, and more particularly concerns a printing machine arranged to reproduce a plurality of transparencies substantially simultaneously.
An electrostatographic printing process involves the formation and utilization of electrostatic latent charge patterns for the purpose of recording and reproducing the patterns in viewable form. The field of electrostatographic printing includes electrophotographic and electrographic printing. Electrophotographic printing is that class of electrostatographic printing which employs a photosensitive medium to form, with the aid of electromagnetic radiation, the electrostatic latent charge pattern. Electrography is that class of electrostatographic printing which utilizes an insulating medium, to form, without the aid of electromagnetic radiation, the electrostatic latent charge pattern. In all of the foregoing machines, it is highly desirable to be capable of reproducing transparencies. More particularly, it is highly advantageous to be capable of reproducing substantially simultaneously a plurality of transparencies on a common copy sheet.
The process of electrophotographic printing will be described hereinafter as an exemplary system for achieving the foregoing. An electrophotographic printing machine exposes a charged photoconductive surface to the light images of the transparencies being reproduced. The irradiated areas of the photoconductive surface are discharged to record thereon electrostatic latent images corresponding to the transparencies. A development system moves the developer mix of carrier granules and toner particles into contact with the photoconductive surface. The toner particles are attracted electrostatically from the carrier granules to the latent image forming a toner powder image thereon. Thereafter, the toner powder image is transferred to a sheet of support material. In many types of electrophotographic printing machines, the sheet of support material is the photoconductive surface and the step of transfer is not required. In either case, a fusing device permanently affixes the toner powder image to the sheet of support material.
Many special purpose electrophotographic printing machines have been developed and are in wide commercial use. For example, electrophotographic printing machines are presently available for reproducing microfilm. In general, a microfilm reproducing machine produces an enlarged copy of a microfilm original. However, high quality reproduction of color slides has only been recently achieved. This process is exemplified by co-pending application Ser. No. 540,617 filed on Jan. 13, 1975, now U.S. Pat. No. 4,027,962, and co-pending application Ser. No. 663,389 filed on Mar. 3, 1976, now U.S. Pat. No. 4,043,656. As described in the foregoing applications, a light image of a color transparency is projected onto a mirror. The mirror reflects the light image through a screen and field lens onto the charged portion of the photoconductive surface. This light image is filtered to record a single color electrostatic latent image on the photoconductive surface. Successive single color electrostatic latent images are recorded and developed with the appropriately colored toner particles. These toner powder images are transferred to a sheet of support material in superimposed registration with one another. This multilayered toner powder image is then permanently affixed to the sheet of support material forming a copy of the color slide being reproduced. Improvements in this process include positioning a mirror in the path of the transparency light image to direct the light image onto the charged portion of the photoconductive member with the mirror being readily removable from the optical light path when opaque original documents are being reproduced. In the foregoing type of transparency reproducing machine, a plurality of size for size copies of the transparency may be formed on a single copy sheet or an enlargement of one transparency may be formed on a single copy sheet. No provision is contained therein for reproducing a plurality of transparencies as enlargements on a common copy sheet.
Accordingly, it is a primary object of the present invention to improve electrophotographic printing machines so as to reproduce a plurality of transparencies as enlargements on a common copy sheet.